Utility knives are hand-held cutting tools capable of a wide range of uses. Typically, a utility knife includes a longitudinal main frame to house either a completely interchangeable blade or a snap-off blade and includes a sliding mechanism attached to the blade. The sliding mechanism moves the blade between an extended position and a retracted position relative to the main frame. The sliding mechanism of the utility knife often includes a resilient engaging member, such as a spring, which engages with a set of tabs formed longitudinally in regular intervals in a groove defined in the main frame that locks the sliding mechanism at a fixed position. A panel located on the sliding mechanism enables a user to slide the sliding mechanism, which carries the blade, to the extended position and the retracted position. Commonly, the blade is a snap-off blade, which has a series of fracture lines and can be broken transversely to expose a new sharp edge portion. Extra blades can be stored in a compartment within the main frame of the utility knife.
In most of the existing devices, the only safety feature provided to hold the blade at the fixed position is the engagement between the resilient engaging member formed on the sliding mechanism and the tabs formed in the groove. Sliding the blade in such a device can be difficult, due to the high friction created between the tabs and the engaging member. Moreover, replacing a new snap-off blade in such a device requires first dissembling and then reassembling substantially the entire utility knife, which is inconvenient to the user.
What is needed is a snap-off blade utility knife having a slide assembly device that can securely lock the blade in position during use, and can be easily slid to a desired extended position for use and to a desired retracted position for storage. It is also desirable to have a snap-off blade utility knife that allows convenient blade replacement.